Background

CD24 (also called Heat Stable Antigen or nectadrin) is expressed on many cell types (Fang et al., 2010), and its expression is dynamically regulated during cellular differentiation (Ayre et al., 2016). CD24 was first described for its role in blocking B lymphocyte (B cell) development. Transgenic mice overexpressing CD24 and CD24 knockout mice exhibit a loss of immature B cells via their increased apoptosis (Hough et al., 1996; Nielsen et al., 1997) demonstrating that altering CD24 expression has serious repercussions in these cells. Additionally, antibody (Ab)-mediated engagement of CD24 induces apoptosis or suppresses proliferation of B cells, depending on their developmental stage (Chappel et al., 1996). CD24 also mediates homeostatic proliferation in T cells (Li et al., 2004), and can negatively regulate inflammation by inhibiting dendritic cell (DC) activation (Chen et al., 2009).